The oxygen ion conductive solid electrolyte has served as the basis of numerous oxygen measuring products. Further, the oxygen ion conductive solid electrolyte cell has served as a device for indirectly measuring the combustibles content of a gas.
In addition to the early work in this area, as evidenced by the teachings of U.S. Pat. No. Re. 28,792, which is assigned to the assignee of the present invention and incorporated herein by reference, more recent applications of the oxygen ion conductive solid electrolyte cell for both oxygen and combustibles measurements are disclosed in the following pending application and issued patent:
1. "Improved Gas Analysis Apparatus", Ser. No. 637,998, filed Dec. 5, 1975; and
2. "Improved Combustibles Analyzer", U.S. Pat. No. 4,158,166, issued June 12, 1979, both assigned to the assignee of the present invention.
While the above implementations of the basic oxygen ion conductive solid electrolyte cell provide effective means for independently measuring oxygen and combustibles, there is disclosed herein with reference to the accompanying drawings a technique whereby a single oxygen ion conductive cell is employed to measure both excess oxygen and excess combustibles content of a monitored gas environment through the use of an electronic circuit responding to a predetermined voltage threshold by switching the cell between a voltage mode and a current mode of operation.